The present invention relates to a method and apparatus for determining one or more physical properties of a rolled smoking article or filter rod. The present invention has particular reference to a method of determining one or more physical properties of a cigarette comprising a tobacco column and an adjacent filter section.
Modern cigarette makers are capable of producing tipped cigarettes at a rate of approximately 8,000-16,000 cigarettes per minute. According to its particular brand, a cigarette should have an accurate predetermined length and circumference. A tipped cigarette comprises a tobacco column comprising compacted, dried and shredded tobacco leaves wrapped in a rolled tube of cigarette paper and an adjacent filter section comprising a cut length of filter rod. The filter section is joined to the tobacco column by means of a piece of tipping paper which is wrapped circumferentially around the filter section to overlap the tobacco column. The filter section of a cigarette should have an accurate, predetermined length and width and, in order to ensure a consistent appearance, the length of the tipping paper (‘overwrap’) should also have an accurate, predetermined length. The cigarette should be substantially free of voids at the interface between the filter section and tobacco column and at the end of the tobacco column remote from the filter section. The cigarette paper should be free of ventilation holes and unwanted markings, and any printed matter, such as words, logos and the like, should be accurately positioned.
As is in the case in many manufacturing processes, there is a need to monitor continually the quality of cigarettes produced on a maker. Conventionally, cigarettes produced by a maker are sampled at random and tested for compliance with predetermined quality standards. In particular, it is common to sample cigarettes manually or automatically and to test the sampled cigarettes for length, circumference, the presence of voids or other defects and ventilation characteristics, such as the pressure drop across the cigarette and/or filter section.
Conventional, industry standard quality assurance/quality control cigarette sampling and testing techniques provide for approximately ten cigarettes to be tested every twenty minutes. In view of the great speed with which cigarettes are produced on a typical maker, this sampling and testing rate is insufficient to achieve visualisation of the process in real time.
EP 1023845 Al (Japan Tobacco Inc) discloses cigarette testing apparatus in which a cigarette is supplied in a horizontal position from a cigarette supplying section to a weight-measuring section where the cigarette weight is measured. The cigarette ejected therefrom is transferred sequentially to a circumference measuring section, a ventilation-characteristic measuring section and a length/hardness measuring section. In the circumference measuring section, the cigarette is received on two juxtaposed rollers which cause the cigarette to rotate about its longitudinal axis. A photosensor comprising a transmitter and receiver, located respectively above and below the rollers, is used to send and receive a slit light between the transmitter and receiver in a direction perpendicular to the axis of the cigarette and to measure a slit light width blocked by the cigarette, thereby to measure the circumference (diameter) of the cigarette. In the length/hardening measuring section, the cigarette is positioned in place by regulating one end of the cigarette, and the position of the other cigarette is measure by use of a photosensor.
U.S. Pat. No. 4,907,607 A (Focke, et al.) discloses apparatus for detecting the presence of voids or other defects in cigarettes by directing light from a light source onto an end face of a cigarette and positioning a light receiver at an angle to the longitudinal axis of the cigarette for detecting light from the light source which is transmitted through at least a portion of the cigarette and exits the cigarette through points other than the end face where the light enters the cigarette.
An object of the present invention is to provide an improved method for determining one or more physical properties of a rolled smoking article or a filter rod, particularly a cigarette comprising a tobacco column and an adjacent filter section.
Another object of the present invention is to provide a method of determining one or more physical properties of a rolled smoking article or filter rod which may be executed sufficiently rapidly to allow the variation in said properties in, for example, cigarettes produced by a maker to be monitor substantially in real time.
In accordance with one aspect of the present invention, therefore, there is provided a method of determining one or more physical properties of a rolled smoking article or filter rod, said method comprising disposing a rolled smoking article or filter rod within a field of view, illuminating said field of view, imaging said rolled smoking article or filter rod within the field of view to form an image, and analysing said image to determine one of more physical properties of the rolled smoking article or filter rod.
In another aspect of the present invention there is provided apparatus for determining one or more physical properties of a rolled smoking article or filter rod, said apparatus comprising:
imaging means defining a field of view, said imaging means being adapted for imaging a rolled smoking article or filter rod in said field of view;
means for positioning a rolled smoking article or filter rod in said field of view;
illuminating means for illuminating said field of view; and
processing means for processing said image to determine said one or more physical properties of a smoking article or filter rod in said field of view.
Preferably said image is a digital image. Said imaging means may comprise a digital camera; preferably a digital video-camera.
Said image may be processed electronically to determine said one or more physical properties. Thus, said processing means may comprise a computer adapted for processing said digital image electronically.
The present invention is thus characterised by forming an image of the rolled smoking article or filter rod in a field of view and processing the image of the rolled smoking article or filter rod to determine said one or more physical properties.
Whilst light of any suitable wavelength may be used for imaging the rolled smoking article or filter rod within the field of view, the rolled smoking article or filter is preferably imaged using infra-red light; more preferably near infra-red light Thus, said imaging means may comprise an infra-red digital video-camera. Preferably said digital video camera has an adjustable shutter-speed for controlling the exposure of the smoking article or filter rod within said field of view, and said imaging means may comprise means for controlling the shutter speed of the camera according to the physical property to be measured and/or the intensity of the illumination provided by said illuminating means. The camera is preferably operated in field mode in order to reduce acquisition time.
Said processing means may be adapted for repeatedly sampling the image, and in some embodiments the computer may be equipped with a frame-grabber such as a PCI frame-grabber for sampling the digital image produced by the camera and for transmitting control signals to the camera and/or said illuminating means.
Said illuminating means may be adapted to cast diffuse light onto the field of view and, in some embodiments, the imaging means may define an optical viewing major axis, and said illuminating means may comprise one or more side-lights which are positioned laterally of the optical major axis. In particular, said illuminating means may comprise two side-lights positioned on opposite sides of the optical axis.
In some embodiments, said illuminating means may comprise a back-light adapted for back-lighting a smoking article or filter rod positioned in the field of view. Said side-lights and back-light may comprise infra-red lights. Preferably, the back-light has a sufficiently high luminosity that infra-red light is transmitted through a rolled smoking article or filter rod positioned in the field of view intermediate the back-light and the imaging means. Said back-light may be adapted to produce a collimated beam.
Preferably the smoking article or filter rod is imaged against a uniformly dark background, such that the edges of the smoking article or filter rod (when viewed in profile) provide high edge contrast without becoming over-exposed.
Preferably said positioning means are adapted for positioning the rolled smoking article or filter rod within the field of view such that the longitudinal axis of the rolled smoking article or filter rod extends substantially orthogonally with respect to the optical major axis. The camera is preferably oriented such that the major axis of the image corresponds to the minor axis of the rolled smoking article or filter rod so that diameter measurements, which have the highest tolerance, are run at maximum resolution, while length measurements, which need not be measured to the same degree of accuracy, are measured at half resolution.
In some embodiments, said positioning means may comprise means for rotating a smoking article or filter rod about its axis in the field of view. Said rotating means may comprise two juxtaposed rollers, which rollers are positioned side-by-side so as to define a groove therebetween, which groove is adapted to receive said smoking article or filter rod, and means for rotating one or both of said rollers, thereby to cause said article or filter rod to rotate.
Said positioning means may comprise means for moving a smoking article or filter rod axially relative to the field of view. Preferably, the moving means comprise means for locating one end of a smoking article relative to the field of view, thereby to establish a known position against which measurements of length can be made.
Said moving means may comprise a pusher adapted to engage one end of a smoking rod or filter rod, and a linear actuator for moving said pusher along a predetermined path, and said locating means may be adapted for indicating the position of said pusher. In some embodiments, said linear actuator may comprise a servo motor for locating said pusher relative to the field of view. Alternatively, a stepper motor having an encoder may be used.
The positioning means may be calibrated by moving the pusher into the field of view, imaging the pusher within the field of view to form an image and processing the image to determine the precise position of the pusher within the field of view. That position of the pusher may be stored as a datum position, so that subsequent movement of the pusher can be related to the datum position for determining the distance between any position of the pusher and said datum position.
Said digital video-camera may comprise a photosensor adapted to form an image consisting of an array comprising a multitude of regularly arranged pixels. Said image sensor preferably comprises a charge coupled device (CCD), but may alternatively comprise any other suitable image sensor such, for example, as a CMOS sensor. Said processing means may conveniently be adapted for measuring distances in said image in terms of pixels, and may be calibrated for converting such pixel distances into actual distances. In some embodiments, said processing means may be calibrated by processing one or more images of one or more objects of accurately known dimensions. In some embodiments the imaging means may be such that the relationship between pixels and actual distances may not be truly linear owing to certain optical effects. Preferably the processing means are therefore calibrated by processing the images of a plurality of objects of different dimensions to compensate for any such non-linear optical effects.
CCD-based cameras suffer from ‘blooming’, whereby excessively bright (over-exposed) objects within the field of view may appear larger than their actual sizes. This effect is caused by saturated elements of the CCD array affecting nearby elements. In addition the interline transfer system employed in a CCD can produce ‘vertical smearing’ of saturated objects. Accordingly, it is important to ensure that the rolled smoking article or filter rod is not over-exposed. An appropriate shutter speed to use for measuring a particular physical property is preferably determined empirically.
In some embodiments, said one or more physical properties may include the length of the rolled smoking article or filter rod. The length of the rolled smoking article may be determined by moving the rolled smoking article or filter rod axially whilst locating one end thereof with respect to the field of view until the other end is disposed within the field of view, and thereafter imaging the rolled smoking article or filter rod to form said image, processing the image to locate said other end with respect of the field of view, and thereafter determining the length of the rolled smoking article or filter rod from the positions of said ends.
Preferably, the rolled smoking article or filter rod is advanced axially until said one end is located at a first predetermined position with respect to the field of view corresponding to a first nominal length of the rolled smoking article of the filter rod, and the other end is disposed within the field of view in the vicinity of a first nominal position corresponding to said first nominal length. The image may then be processed to determine the actual position of the other end, and the length of the rolled smoking article or filter rod calculated by determining the difference between said first nominal and actual positions and adding or subtracting that difference to or from the first nominal length. Said image may be processed within a first region of interest within said field of view, which first region of interest encompasses all likely actual positions of said other end of the rolled smoking article or filter rod when said one end is located at said first predetermined position. By limiting processing of the image to the first region of interest in which said other end of the rolled smoking article or filter rod is expected to be disposed, the image can be processed more quickly, without having to process the entire image of the field of view. The position of said other end may be calculated using horizontal and vertical region projections of said region of interest; the resulting projections may be analysed in order to detect any significant edges within the region of interest, which will correspond to said other end. The same technique may be used for detecting other edges as described below.
Thus, the apparatus in accordance with the present invention may further comprise control means for controlling said moving means and said processing means, said control means comprising a database adapted to store a first nominal length for the rolled smoking article or filter rod and being adapted to control said moving means to move the one end of the rolled smoking article or filter rod to a first predetermined position with respect to the field of view corresponding to the first nominal length, such that the other end is disposed within the field of view, and thereafter to control the processing means to process the image to locate said other end with respect of the field of view and to determine the actual length of the rolled smoking article or rod from the locations of said one and other ends.
Preferably said control means are adapted to derive a first nominal position for said other end within the field of view when the one end is positioned at the first predetermined position, said first nominal position corresponding to said first nominal length, and said processing means may be adapted to locate the actual position of the other end and calculate the difference between the actual and nominal positions, the length of the rolled smoking article or filter rod being equal to the first nominal length plus or minus the difference. Said control means may further be adapted to derive a first predetermined region of interest in the field of view, which encompasses all likely positions of the other end of the rolled smoking article or filter rod, when said one end is positioned at the first predetermined position, and said processing means may be controlled to process said image within the first predetermined region of interest to locate said other end.
Known image-processing techniques may be used for processing the image to determine accurately the position of the other end of the rolled smoking article or filter rod in the field of view. Those skilled in the art are familiar with image processing algorithms for detecting edges in digital images, including algorithms which measure contrast levels for defining a point at which an edge is defined as being present, the length (in pixels) along an edge which is used to determine a contiguous and true edge, and algorithms for carrying out statistical probability calculations to confirm (or otherwise) that a detected edge is a true edge. As described above, a preferred technique for detecting the position of a feature within a region of interest comprises generating horizontal and vertical region projections of a region of interest, and then analysing said projections in order to detect any significant edges within the region of interest, which will correspond to the feature being measured. Such imaging processing techniques are not described further herein, but are described in detail in a number of standard reference works including Sonka, et al., 1999, Image Processing, Analysis, and Machine Vision, 2nd Edition, page 256 (6.35), Pacific Grove: PWS Publishing, ISBN 0-534-95393-X, the contents of which are incorporated herein by reference. By imaging the rolled smoking article or filter rod against a dark background, relatively fast shutter speeds can be used for acquiring images for detecting external edges such as said other end, thereby avoiding or reducing any undesirable blooming effect. An appropriate shutter speed should be determined empirically on a product sample to avoid over-exposure.
In some embodiments, said rolled smoking article or filter rod may comprise one or more intended visible external features intermediate its opposite longitudinal ends, the or each feature having a different colour of shade from the immediately adjacent portion or portions of the article or rod, rendering the edge of edges of the or each feature visible by contrast with said adjacent portion(s). It is generally desirable that such intended features should be positioned accurately on the article or rod, and the position of such a feature is usually specified by reference to a reference end of the article or rod. A rolled smoking article typically has first and second adjacent longitudinal sections and an outer tipping layer which extends axially from a first end of the rolled smoking article over one of said first and second sections and overlaps the interface between said sections to cover partially the other section, said outer tipping layer terminating remote from said first end in an edge. The length of the overwrap is usually specified by reference to the first end and is thus equal to the distance between said first end and the edge. Said outer layer may have a significantly different colour or shade from the other section, rendering said edge visible. A cigarette, for example, typically comprises a first tobacco column and a second adjacent filter section and an outer layer of tipping paper which extends from the first end of the cigarette over the filter section to overlap the interface between the tobacco column and filter section to cover partially the tobacco column. Said outer tipping layer commonly has a different colour from the first tobacco section. A smoking article or filter rod may also comprise printed matter on its outer surface between said opposite ends, such as one or more letters, numerals, words, logotypes, and the like, or a combination of these, which matter may be printed using one or more inks having a different colour or shade from the immediately adjacent portion(s) of the article or rod, rendering the edge or edges of the printed matter visible by contrast.
In accordance with the present invention, said image may be processed to determine the axial position or positions of one or more such external features with respect to a pre-specified reference end of the rolled smoking article or filter rod.
The axial position of such an external feature may be determined in accordance with the present invention by determining the axial orientation of the rolled smoking article or filter rod with respect to said reference end, advancing the rolled smoking article or filter rod axially whilst locating said one end thereof with respect to the field of view until the feature is disposed within the field of view, imaging said rolled smoking article or filter rod to form said image, processing the image to locate said feature with respect to the field of view, and thereafter determining the axial position of the feature with respect to said reference end from the position of the edge, the position of said one end and, depending on the axial orientation of the rolled smoking article or filter rod, the length of the rolled smoking article or filter rod.
Preferably, the rolled smoking article or filter rod is advanced axially until said one end is located at a second predetermined position with respect to the field of view corresponding to a first nominal distance between said feature and the one end of the rolled smoking article or filter rod, and the feature is disposed within said field of view within the vicinity of a second nominal position corresponding to said first nominal distance. Said image may be processed to determine the actual position of said feature, and the actual distance between the feature and the one end of the rolled smoking article or filter rod may be determined by calculating the difference between said second nominal and actual positions and adding or subtracting that difference to or from the first nominal distance, the axial position of the feature with respect to the reference end being equal to said actual distance or, depending on the axial orientation of the rolled smoking article or filter rod, the length of the rolled smoking article or filter rod minus the actual distance. Said image may be processed within a second limited region of interest in the field of view, which second region of interest encompasses all likely actual positions of the feature when said one end is located at said second predetermined position.
Suitably the database of the apparatus in accordance with the present invention may be further adapted to store user-inputted data indicating the axial orientation of the rolled smoking article or filter rod. A rolled smoking article or filter rod having a visible external feature between its opposite longitudinal ends may be directional, in the sense that the rolled smoking article or filter rod is rotationally asymmetrical when turned through 180° about a point mid-way between said opposite longitudinal ends. Thus, the rolled smoking article or filter rod may be conveyed by said moving means, with either of said longitudinal ends first, and for that reason said processing means may be adapted, as mentioned above, to receive user-inputted information concerning the axial orientation of a rolled smoking article or filter rod to be tested.
Said database forms an important feature of the present invention in that the physical properties of a rolled smoking article, e.g. a cigarette, or filter rod, such as its length, circumference, etc. vary from brand to brand. The database in accordance with the present invention may comprise nominal information for a plurality of different brands of cigarette, including said first nominal length and said first nominal distance, and said processing means may be adapted to receive user-inputted data identifying the particular brand of rolled smoking article or filter rod to be tested, so that the correct nominal values can be selected and used by said control means.
Thus, said database may be adapted to store a nominal axial position of said feature with respect to said reference end, and said control means may be adapted to derive from the nominal axial position and, depending on the axial orientation of the rolled smoking article or filter rod, the first nominal length, said first nominal distance between said feature and said one end of the rolled smoking article or filter rod, and to control the moving means to move the rolled smoking article or filter rod to the second predetermined position with respect to the field of view corresponding to said first nominal distance, such that said feature is disposed within the field of view, and thereafter to control said processing means to process the image to locate said feature with respect to the field of view and determine the actual axial position of the feature from the position of the feature, the position of the one end and, depending upon the orientation of the rolled smoking article, the actual length of the rolled smoking article.
Preferably, said control means are further adapted to derive from the nominal axial position and, depending on the axial orientation of the rolled smoking article or filter rod, the first nominal length, said second nominal position for said feature with respect to the field of view, when said one end is positioned at said second predetermined position, and said processing means may be adapted to locate the actual position of said feature with respect of the field of view and to determine the actual distance between said feature and said one end by calculating the difference between said actual and second nominal positions and adding or subtracting that difference to or from the first nominal distance, the actual axial position of said feature with respect to said reference end being equal to the actual distance or, depending on the orientation of the rolled smoking article or filter rod, the actual length of the rolled smoking article or filter rod minus the actual distance.
Said control means may be adapted to derive said second predetermined region of interest of said field of view which encompasses all likely positions of the feature of, when said one end is positioned at said second predetermined position, and said processing means are controlled to process said image within said second predetermined region of interest to locate said feature.
When said rolled smoking article or filter rod comprises a rolled smoking article, such for example as a cigarette, comprising an outer tipping layer that extends from said first end over one of the first and second adjacent sections to overlap the other section, said feature preferably comprises said edge of the outer tipping layer. Said first end is preferably nominated as said reference end, and the axial position of said edge with respect to said reference end is the length of the tipping layer between said first end and said edge. The nominal axial position of said edge with respect to said reference end which may be stored by said database is a second nominal length for said outer tipping layer.
Alternatively said feature may comprise printed matter on the outer surface of rolled smoking article or filter rod as described above. In particular, said feature may comprise a characteristic feature of an item of printed matter, for example a pre-defined point of character or graphic device. If the printed matter comprises a plurality of individually printed items then the axial position of each item may be determined in accordance with the present invention.
According to a particular aspect of the present invention, said processing means may be adapted for repeatedly sampling the image as a rolled smoking article or filter rod is rotated by said rotating means and for processing each image sample to measure the diameter of said rolled smoking or filter rod in each image sample and using the measurements to obtain one or more physical properties of said rolled smoking article or filter rod selected from the mean diameter, ovality, circumference, roundness and shape of said rolled smoking article or filter rod.
The diameter of the rolled smoking article or filter rod in each image sample may be obtained by processing the sample to locate the two opposite edges of the rolled smoking article or filter rod in profile and calculating the distance between said opposite edges. Each image sample may be processed within two predetermined, laterally spaced regions of interest of said field of view to locate said two opposite edges, which regions of interest are determined on the basis of a nominal diameter of the rolled smoking article or filter rod.
Said database may thus be adapted to store the nominal diameter of the rolled smoking article or filter rod, and said control means may be adapted to define said two laterally spaced regions of interest of the field of view corresponding to the nominal diameter, each of which regions of interest encompasses all likely positions of a respective one of the opposite edges, and said control means may be configured to control the processing means to process each image sample within said two regions of interest to locate said opposite edges.
Preferably the diameter of the rolled smoking article or filter rod is measured at two more axially spaced locations on said rolled smoking article or filter rod. Where the rolled smoking article or filter rod comprises a rolled smoking article comprising first and second adjacent longitudinal sections, such as a cigarette comprising a tobacco column and an adjacent filter section, it is preferred that the diameter of each section should measured separately.
Said rolled smoking article or filter rod may comprise one or more circumferential markers adapted to indicate the rotational orientation of the rolled smoking article or filter rod, and said processing step may include processing the samples to determine a complete revolution of the rolled smoking article or filter rod. Thus, said processing means may be adapted to detect one or more circumferential markers on a rolled smoking article or filter rod, and said control means may be adapted to control said rotating means in response to output from the processing means such that rolled smoking article and filter rod is rotated through a complete revolution.
In a particular aspect, the present invention comprehends determining the axial direction of a rolled smoking article which is rotationally asymmetric as described above, such that the rolled smoking article is directional and comprises at least one outer layer which is wrapped circumferentially around the rolled smoking article to overlap itself thereby to form a longitudinal seam. The image samples may be processed to determine the wrapping direction of the outer layer relative to direction of the rolled smoking article. In particular, said image sample may be processed to determine the position of the longitudinal seam by detecting the position of a shadow cast by said seam as the rolled smoking article rotates. Each image sample may be processed in accordance with the present invention to detect the presence of said shadow in two predetermined, laterally spaced regions of interest in the field of view, the presence of said shadow in one or other of said regions of interest being determinative of the direction of wrapping of the outer layer, the regions of interest having been determined on the basis of the nominal width of the rolled smoking article.
Preferably, said infra-red side-lights are arranged for illuminating said rolled smoking article obliquely to enhance the shadow cast by said seam.
Said processing means may therefore be adapted for repeatedly sampling the image as said rolled smoking article is rotated by said rotated means and processing each sample to detect the position of the shadow cast by the longitudinal seam of the outer layer. Said database may be adapted to store said nominal diameter of the rolled smoking article, said control means being adapted to derive two laterally spaced regions of interest of said field of view based on said nominal width, each of said regions of interest encompassing all likely positions of said shadow depending on the direction of wrapping of the outer layer and to control said processing means to detect the presence of the shadow in one of the regions of interest.
A rolled smoking article may comprise two or more outer layers, each of which outer layers is wrapped circumferentially around the rolled smoking article to overlap itself to form an axially extending seam, and in a particularly advantageous aspect of the present invention said image may be processed to determine the wrapping direction of each outer layer relative to the direction of rolled smoking article.
Many modern cigarette makers are adapted to manufacture cigarettes in two parallel lines. In each line, tobacco columns are formed by wrapping cigarette paper circumferentially around measured portions of tobacco. As described above, the cigarette paper is wrapped around each rod to overlap itself and form a longitudinal seam. The tobacco columns in each stream are then tipped in the conventional fashion by inserting a double-length piece of filter rod between two tobacco columns and then over-wrapping the filter rod with tipping paper to join the filter rod section to each of the tobacco columns, the filter paper overlapping each of said tobacco columns. The filter rod is then guillotined to form two complete cigarettes. The filter paper is wrapped around the filter section and two adjoining tobacco columns in opposite directions on the two lines of the maker. Accordingly, when the cigarettes are guillotined, there are four possible permutations of direction of wrapping of the cigarette paper and tipping paper.
By determining the respective directions of wrapping of the two outer layers relative to the axial direction of the rolled smoking article in accordance with the present invention, the particular line of a maker on which the rolled smoking article was made can be identified. It will be appreciated that this is important because the physical properties of cigarettes made on the two lines of the maker may vary differently with time a, and when the finished cigarettes from the two lines are sampled and tested, it is important to know from which line a given cigarette originates.
Thus, said processing means may be adapted to determine the respective wrapping directions of two or more outer layers of the rolled smoking article, each of which outer layers is wrapped circumferentially around the rolled smoking article to overlap itself to form an axially extending seam.
In addition to intended visible external features which are positioned with reference to a reference end, a rolled smoking article or filter rod may also comprise one or more intended visible external patterns which are not positioned with respect to such a reference end, but comprise a regularly repeating design, said design comprising one or more features which are visible by contrast with the immediately adjacent portions of the rolled smoking article or filter rod. For example, the cigarette paper used to wrap a tobacco column often comprises a plurality of regularly axially spaced, circumferential, relatively dark bands of prescribed thickness and spacing. Typically the nature of such bands is characteristic of the paper and may vary from one brand or variety of cigarette to another.
In accordance with another aspect of the present invention, said processing means may be programmed to analyse said image obtained by said imaging means to locate two adjacent design repeats of such a pattern and to measure the pitch between corresponding features of the two repeats.
In some embodiments, the processing means may be programmed to measure one or more characteristic dimensions of the design between two or more features of a single design repeat.
Preferably said pitch and characteristic dimension(s) are measured axially with respect to the rolled smoking article or filter rod.
Said processing means may be further programmed to compare said pitch or characteristic dimension(s) respectively with a corresponding nominal pitch and nominal characteristic dimension(s) stored in said database and to generate an alarm signal if a measured pitch or characteristic dimension is not substantially the same as the corresponding nominal pitch or dimension within a predetermined margin of error.
For example, said processing means may be adapted to locate the respective axial positions of the two opposite edges of each of two adjacent circumferential bands on a cigarette paper of the kind described above, and to measure the pitch between corresponding edges of the two bands, and the axial thickness between the two opposite edges of the same band. A wrong pitch and/or dimension might indicate that an incorrect stock of paper has been used.
In another aspect of the present invention, said rolled smoking article or filter rod may be back-lit to reveal internal physical properties of the rolled smoking article or filter rod, and said image may be processed to determine said physical properties. As mentioned above, said rolled smoking article or filter rod is preferably back-lit with infra-red light. Said processing means may be adapted to detect any voids in the rolled smoking article or filter rod, said voids may be apparent in the image as areas of unusually greater brightness where the translucency of the rolled smoking article or filter rod is increased owing to the absence or dearth of tobacco or filter material in the void. Since the back-light is able to penetrate paper easily, the camera may be set to a relatively fast shutter speed for the detection of voids. Voids may be detected in the image as bright spots using basic segmentation as disclosed by Sonka, et al., 1999, ibid at pages 124-128, after the image has been ‘thresholded’ using a bimodal histogram threshold detection algorithm as described by Ridler, et al. in Picture Thresholding Using an Iterative Selection Method, IEEE Transactions on Systems, Man and Cybernetics, 1978; 8(8): 630-632.
Said rolled smoking article or filter rod may comprise a rolled smoking article having a tobacco column and an adjacent filter section, and for the majority of kinds of filter rod, said rolled smoking article may be illuminated to show an internal end face of filter section at the interface between said column and said section, and said image may be processed to determine the length of the filter section between said end face and the other end of the filter section at the end of the rolled smoking article. This operation requires very low shutter speeds, such that as much light as possible is able to penetrate the filter rod. This may lead to some overexposure of the image; however, the inaccuracies caused by any apparent blooming of the image are expected to lie within required tolerances for this measurement. Vertical smearing is not significant due to the projection technique used to locate edges within an image.
It will be appreciated that the internal end face of the filter section is a feature which is visible externally when the rolled smoking article is back-lit, and thus the axial position of said end face with respect to said other end of the filter section, which is the length of the filter section, may be determined substantially as described above. Thus the length of the filter section between the internal end face and said other end may be determined by determining the axial orientation of the rolled smoking article, moving the rolled smoking article axially whilst locating one end thereof with respect of the field of view until the end face is disposed within the field of view, imaging the rolled smoking article to form said image, processing the image to locate said internal end face with respect to the field of view, and thereafter determining the length of the filter section from the positions of the one end and of the end face and, depending on the orientation of the rolled smoking article, on the length of the rolled smoking article.
Preferably the rolled smoking article is advanced axially until the one end is located at a third predetermined position with respect to the field of view corresponding to a second nominal distance of the internal end face from said one end, and the internal end face is disposed within the field of view in the vicinity of a third nominal position corresponding to said second nominal distance. The image may then be processed to determine the actual position of the internal end face and thus the actual distance between said internal end face and the one end by calculating the difference between the third nominal and actual positions and adding or subtracting that difference to or from the second nominal distance, the length of the filter section being equal to the said actual distance or, depending on the axial orientation of the rolled smoking article, the length of the rolled smoking article minus the actual distance.
Said image may be processed within a third limited region of interest of the field of view, which third region of interest encompasses all likely positions of the internal end face when said one end is located at said third predetermined position relative to said field of view or said datum position.
Said database may therefore be adapted further to store a third nominal length of the filter section, and the control means may be configured to derive from the third nominal length and, depending on the axial orientation of the rolled smoking article as indicated by user-inputted data, the first nominal length, a second nominal distance between an internal end face of the filter section at the interface between said filter section and said tobacco column and said one end of the rolled smoking article, and to control the moving means to move the rolled smoking article to the third predetermined position with respect to the field of view corresponding to the second nominal distance such that said internal end face is disposed within said field of view, and thereafter to control said processing means to process said image to locate said internal end face with respect of the said field of view and determine the actual length of the filter section from the position of the internal end face, the position of the one end and, depending upon the orientation of the rolled smoking article, the actual length of the rolled smoking article.
Preferably said control means are further adapted to derive from said third nominal length and, depending on the axial orientation of the rolled smoking article, the first nominal length a third nominal position for said internal end face with respect to the field of view when said one end is positioned at said third predetermined position and said processing means are adapted to locate the actual position of the internal end face with respect of the field of view and determine the actual distance between the internal end face and said one end by calculating the difference between the actual and third nominal positions and adding or subtracting that difference to or from the second nominal distance, the actual length of the filter section being equal to the actual distance or, depending on the orientation of the rolled smoking article, the actual length of the rolled smoking article minus the actual distance.
Said control means may be further adapted to derive a third predetermined region of interest of said field of view which encompasses all likely positions of the internal end face, when said one end is positioned at said third predetermined position, and said processing means may be controlled to process said image within said third predetermined region of interest to locate said internal end face.
In some embodiments, as described above, said rolled smoking article may further comprise an outer tipping layer extending axially from said first end of the rolled smoking article over said second filter section and including an overlapping portion that overlaps the interface between said tobacco section and said tobacco column to cover partially the tobacco column, and said image may be processed to determine the axial length of said outer tipping layer (the ‘overwrap’) and the length of said overlapping portion (the ‘overlap’) may be calculated from the difference between the overwrap and the length of the filter section.
Thus said processing means may be further adapted to determine the axial length of the outer tipping layer which extends axially form the first end of the rolled smoking article over the second filter section and includes an overlapping portion that overlaps the interface between the filter section and the tobacco column to cover partially the tobacco column and has an appearance which is distinct from that of the remaining non-overlapped portion of the first section, thereby to determine the length of the overlapping portion by calculating the difference between the length of the outer tipping layer and the length of the filter section.
In another aspect of the present invention there is provided apparatus for determining one or more physical properties of a rolled smoking article having a tobacco column, an adjacent filter section, an outer layer being wrapped circumferentially around said tobacco column to overlap itself thereby to form a first longitudinal seam, and an outer tipping layer, said tipping layer being wrapped circumferentially around said rolled smoking article to overlap itself thereby to form a second longitudinal seam and extending axially form a first end of the rolled smoking article over said filter section, overlapping the interface between said filter section and said tobacco column to cover partially the tobacco column and terminating remote from the first end in an edge, and having an appearance that is distinct from that of the remaining non-overlapped portion of the tobacco column, said apparatus comprising:
imaging means defining a field of view, said imaging means being adapted for forming a digital image of said rolled smoking article in said field of view;
positioning means for positioning said rolled smoking article in said field of view, said positioning means comprising means for rotating said rolled smoking article about its axis in said field of view and means for moving said rolled smoking article axially relative to the field of view;
means for locating one end of the rolled smoking article relative to the field of view;
illuminating means which are selectively operable for casting diffuse light on to said field of view for illuminating said field of view, and/or for back-lighting the rolled smoking article positioned within the field of view;
processing means which are adapted for sampling said digital image and processing said image samples to determine one or more physical properties of the rolled smoking article in said field of view;
a database adapted to store a first nominal length of the rolled smoking article, a second nominal length of the tipping layer between the edge and the first end, a third nominal length of the filter section, and user-inputted data indicating the axial orientation of the rolled smoking article on the positioning means; and
control means for controlling said moving means, said rotating means, said illuminating means and said processing means, said control means being configured to:
(i) control said moving means to move the one end of the rolled smoking article or filter rod to a first predetermined position with respect to the field of view corresponding to said first nominal length, such that the other end of the rolled smoking article is disposed within the field of view, and thereafter to control said processing means to process said image to locate said other end with respect to the field of view and to determine the actual length of the rolled smoking article from the locations of said one and other ends;
(ii) control the processing means to process the image to locate two opposite edges of the rolled smoking article in profile and to calculate the distance between said opposite edges;
(iii) derive from said second nominal length and, depending on the axial orientation of the rolled smoking article, the first nominal length, a first nominal distance between said edge and said one end of the rolled smoking article, and to control the moving means to move the rolled smoking article to a second predetermined position with respect to said field of view, corresponding to said first nominal distance, such that said edge is disposed within said field of view, and thereafter to control said processing means to process said image to locate said edge with respect to said field of view and determine the actual length of the tipping layer from the position of the edge, the position of the one end and, depending on the orientation of the rolled smoking article, the actual length of the rolled smoking article;
(iv) control said rotating means to rotate said rolled smoking article about its axis and to control said processing means to sample repeatedly said image as said rolled smoking article is rotated and to process each sample to detect the position of a shadow cast by the first longitudinal seam of said outer layer, thereby to determine the direction of wrapping of said outer layer relative to the direction of the rolled smoking article;
(v) control said rotating means to rotate said rolled smoking article about its axis and to control said processing means to sample repeatedly said image as said rolled smoking article is rotated and to process each sample to detect the position of a shadow cast by the second longitudinal seam of the tipping layer, thereby to determine the direction of the wrapping of the tipping layer relative to the direction of the rolled smoking article;
(vi) derive from the third nominal length and, depending upon the axial orientation of the rolled smoking article, the first nominal length, a second nominal distance between an internal end face of a filter section at the interface between said filter section and said tobacco column and said one end of the rolled smoking article, and to control the moving means to move the rolled smoking article to a third predetermined position with respect to the field of view corresponding to said second nominal distance, such that said internal end face is disposed within said field of view and thereafter to control the processing means to process the image to locate said internal end face with respective to the field of view and determine the actual length of the filter section from the position of the internal end face and, depending on the orientation of the rolled smoking article, the actual length of the rolled smoking article; and
(vii) control said processing means to determine the axial length of the overlapping portion of the tipping layer by calculating the difference between the length of the outer tipping layer and the length of the filter section.
Preferably said moving means may comprise a pusher which is adapted to engage said one end of the rolled smoking article for pushing said rolled smoking article axially relative to the field of view. Said apparatus may be calibrated to establish a datum position of said pusher relative to the field of view, and said first, second and third predetermined positions may be specified by reference to the datum position.
In addition to intended visible external features, a rolled smoking article or filter rod may undesirably comprise unwanted visible external features such as spot marks and ventilation holes. Such features may be revealed in said image of the rolled smoking article or filter rod obtained by said imaging means as one or more discreet dark areas in contrast to the surrounding areas of the rolled smoking article or filter rod, and may appear at random positions.
In accordance with another aspect of the present invention said processing means may be adapted to detect the presence of one or more unwanted visible external features by generating a contrast map for a region of said rolled smoking article or filter rod, comparing said contrast map with a reference contrast map for said region, and identifying any unexpected areas of significantly different contrast.
An unwanted visible external feature may be identified as an unexpected area of significantly greater contrast than a corresponding area of the reference map.
In some embodiments, a plurality of contrast maps of said rolled smoking article or filter rod may be generated serially as the rolled smoking article or filter rod is moved by said moving means through, or rotated by said rotating means in, the field of view of said imaging means, and each map may be compared with a corresponding reference map.
Said database may store said reference contrast maps. Preferably, said database stores a representative contrast map for each different kind of region of said rolled smoking article. Thus the database does not need to store a reference map for the whole smoking article or filter rod, but where a smoking article comprises a plurality of adjacent sections of different colour or shade, or having a different pattern, for example, the database may comprise representative a reference contrast map for each section.
In yet another aspect of the present invention, there is provided a method of monitoring the variation in physical properties of cigarettes produced on a maker substantially in real-time by serially sampling cigarettes produced by said maker and determining one or more physical properties of said serially sampled cigarettes in accordance with the present invention. The values of said one or more physical properties may be output with respect to the time of sampling and may be used, for example, to generate a graphical display of the variation of said one or more physical properties with time in cigarettes produced by the maker. Where said maker comprises two lines of cigarettes which are merged prior to packaging, the present invention comprehends serially sampling cigarettes from said merged lines and determining inter alia from the respective directions of wrapping of the said tipping and cigarette papers the line on which a given cigarette was made and associating the one or more physical properties of the cigarette with that line.